The invention concerns separators which separate one material from another based on their relative densities. In a domestic context a cyclone-based vacuum cleaner is a separator for separating dirt and dust particles from air. Similar devices are employed in industrial and commercial processes, in laboratories and in clinical and hospital environments for separating particulate material from fluidsxe2x80x94normally air or gaseous mixture; or particulate material for liquids. In particular, but not exclusively the invention is applicable to vacuum cleaners in which one or more cyclones are set up within the apparatus for the purpose of efficiently separating dust and dirt particles from an incoming airstream.
In the separator/vacuum cleaner shown in PCT/GB98/03306, the collector 14 receives dust and dirt particles which have been separated by the secondary cyclone effect in the conical chamber 73. Dust and particles from the primary cyclone separation effect in the region 13, are collected in region 31 of collector 32, and when the level of the dust and particles in 31 gets close to the flange 21, the collector 32 must be emptied.
For satisfactory operation, the interior of 14 must be kept separate from 31.
However in practice it is found that even when 31 is full, the volume of dust and dirt particles in 14 is a small fraction of that in 31, and the useful volume of 32 is very substantially reduced by the secondary cyclone collection chamber 14.
It is an object of the present invention to provide an improved particle collecting arrangement for collecting particles from two separation stages of a multistage air/particle separator.
1. According to the present invention apparatus for separating particulate material from an airstream established by suction, comprises:
(1) a primary separation chamber in which particles are separated from the airstream therein by centrifugal force;
(2) a main particle collecting region into which the particles separated by the primary separation can fall under gravity;
(3) a secondary separation chamber downstream of the primary chamber, to which air and particles not separated in the first chamber, pass;
(4) an air outlet in the secondary chamber through which air substantially free of particles can exit;
(5) an intermediate particle collecting region associated with the secondary chamber, in which particles collect after separation by centrifugal force from the air flowing through the secondary chamber;
(6) a valve between the intermediate particle collecting region and a second particle collecting region, which is closed while air flows through the apparatus but which is opened when airflow ceases to allow particles in the intermediate region to pass into the second region.
The second collecting region may be separate from the main particle collecting region, but advantageously the main particle collecting region also comprises the second particle collecting region.
The valve means is operable manually, or electrically, but preferably the valve operates in response to the flow of air through the apparatus so as to become closed when the air flow reaches and exceeds a given rate of flow, and opens when air fluid flow falls below a given rate of flow.
The valve may comprise a ball valve comprising a captive lightweight ball which is lifted by the airflow to close an orifice at one end of the secondary chamber, and which will fall back under gravity to open the orifice when the airflow ceases.
A baffle may be provided downstream of the valve to reduce the tendency for material beyond the valve to be sucked back through the valve while the air flow is being established.
A baffle may be located between the intermediate and second regions to create a tortuous path for particulate material therethrough.
In either event the baffle may comprise a helix.
The entry point of the helix may be spaced from the exit from the secondary separation chamber.
The gap between the entrance to the helix and the exit from the secondary separation chamber is in the range 4 to 6.4 mm.
The helix may have two complete turns.
Typically a gap of the order of 4 mm exists between the ball and the valve seating, when open.
The valve seating may include an annular seal so that when the ball is held thereagainst by suction, there is no tendency for air to leak past the ball.
Alternatively the closure member may present a conical or frusto-conical surface to an annular seating, which preferably includes an O-ring seal for engagement by the said surface to close the valve.
A spring may to advantage be provided acting on the ball or other closure in a direction to open the valve.
Preferably a level sensing device is provided in the or each particle collecting region to indicate when the contents of the collecting region has reached a given level, requiring it to be emptied.
The sensing device typically includes a switch for generating an alarm and/or interrupting the power supply to the suction producing means.
The invention is not limited to apparatus for separating particles from air but may be employed in apparatus operating in a similar way to separate particulate material from a liquid (where the particulate material is more dense than the liquid) or one liquid from another liquid (again where there is a difference in density of the two liquids).